Signaling system



Nov. 8, 193 J. L. FINCH- 1,837,237

' SIGNALING SYSTEM 7 Filed May 31, 1929 S Sheets-Sheet 1 "Hill" INVENTOR J. L. F'lNCH ATTORNEY Nov. 8, 1932.

.|.- L. FINCH SIGNALING SYSTEM Fild ma :51. .1929

' 3 Sheets-Sheet 2 E C:=EEEEEE===2E5: ANN

INVENTOR JL FINH ATTORN EY Nov.

UNITED STATES PATENT OFFICE JAMES L. FINOH, OF ROCKY POINT, NIH YORK, ASB IGNOR T0 RADIO CORPORATION OF 'AMERICA, A CORPORATION OF DELAWARE SIGNALING SYSTEM Application filed May 31, 1929. Serial No. 887,199.

This invention relates to a signaling system and has for one of its objects the provision of a new method and means for signaling.

In radio telegraphy it has been, common practice to make'use of transmitters which are adapted to radiate at constant amplitude energy of constant frequency only. Accordingly they could be built very inexpensively; but, this advantage is ofiset to a great extent where it isdesired to multiplex or send a plurality of signals over a single channel.

Heretofore multiplexing required some method such as the amplitude modulation of the high frequency transmitter output as in a broadcast transmitter, the division of time between the various channels as is used on some trans-ocean cables, the radiation of a number of slightly different frequenciessimultaneously as in sin le side band telephony or the shifting of t e frequency within a given band at an audio or superaudio rate.

All of these methods involved the use of much more expensive equipment than this invention will require.

A more specific object of this invention is,-

therefore, to provide a method and means whereby a simple transmitter such as is now only suitable for telegraphy may be utilized for the multiplexing of signals. Briefly the manner in which thls object is accomplished is by energizing the transmitter at constant frequency intermittently for periods of time bearing a definite relation to the algebraic amplitude of a signal wave, the wave being either a single signal wave or the composite of a plurality of signal waves.

. In accordance with the practice of the United States Patent Ofiice, the novel features of this inventionare defined in the appended claims. However, the invention may best be understood both as to its structure and mode of operation by referring to the accompanying drawings in which,

igure 1 is a wiring diagram showing the manner in which a transmitter may be energized at time intervals corresponding to the amplitudes of a signal wave;

Figure 2 dia reconfirm mnv in. m.....:..,:

be utilized Now, if a radiating antenna, for example,

is energized at constant frequency and am litude for short lengths of time the duration varying according to the successive am litudes of the composite wave 8, the excitationtime curve of the antenna will be as illustrated in Figure 4. Figure 4 and Figure 3 have the same time axis.

At a receivin station, by the provision of a suitable recti curve 8 can be simulated by the reception of energy transmitted in accordance with the curve of Figure 4; and, by the additional provision of suitable filters, each of the signal waves 2, 4:, 6, may be obtained which ma to actuate independent recor ing devices, thereby reproducing the original signals.

The means for energizing the transmitting antenna according to the curve illustrated in Figure 4 is diagrammatically indicated in- Figure 1.- At A there is indicated means whereby a composite wave may be obtained from a plurality of individually modulated wave sources. v

A wave is generated at B which has a frequency several times as high as the highest frequency which goes to make up the composite wave. This wave has a special form, its voltage gradually building up at a uniform rate and then dropping again practically instantaneously. 4

The voltage waves generated at A are added to those generatedat B and are impressed upon the circuits D. The circuits D are constructed so that their output is a voltage wave At LL 1.- m

er and filter, the composite,

is rectangular in form, its voltage swinging sharply between two values, the duratlon of this voltage at one of these values be ng pro portional to the value of the composite wave generated at A.

More particularly there is shown at A a lurality of tone generators 2', 4', 6' generatmg different frequency currents corresponding to the frequencies of curves 2, 4, 6, of F 1gure 3. By the use of keys 10, the waves generated'by the tone generators may be suitably chopped or modulated and fed into combming tube 12 which is suitably biased by potential source 14. In the output circuit of electron discharge device 12 there will be a potential wave corresponding to the com osite wave 8 of Figure 3, this potential, as s own,

, being fed to'the control electrodes of electron discharge device 36, where it is added to the potential from B. y

At B there is illustrated a vdot generator which generates a. carrier wave having a rela-' tively low frequency relative to radio frequency currents and of a relatively high frequency relative to a frequency of the current generated by generators'2', 4, 6. The dot generator consists of a glow discharge tube rectifier having connected in series therewith a souce of potential 22, a resistance 24 and a choke 26. Across choke 26 and rectifier V 20 there is placed a condenser 28.

It will thus be seen that potential slowly builds up across the terminals of condenser 28 g and, when the potential becomes of suflicient value to break down rectifier 20, there is a sudden discharge across rectifier 20 which continues by virtue of choke 26 past the zeropotential point of condenser 28. The wave form of the potential generated is illustrated in Figure 5, this potential being applied through suitable condensers 30, 32 to the control electrode of electron discharge device 36.

The voltage impressed on grid 42 of tube 36 by circuits A and B is illustrated in Figure 6. This voltage results from the combi nation-of the wave generated at B, which, as shown in Figure 5, has substantially linear sloping and vertical boundaries, and the,com positewave from A.- As shown in Figure 6, the voltage applied to grid 42 may be considered the voltage generated at B shifted so that its axis simulates the composite from A;'o r it may be considered the algabraic resultant of waves from A and B.

' The grid of tube 3.6 is maintained, through resistance 38 the secondary of transformer 34 and potential '-was of source 40, highly negative. Because of the' high negative bias. on the control electrode 42 of electron discharge device 36,1ittle or no current will flow thr'ou h the resistance 44 in the anode circuit of tuie In parallel with resistance 44 is a glow discharge device 46 which allows current to flow therethrough only after a certain value of potential is applied across its terminals. In series with discharge device 46 is a resistance 48 which, when a current flows through de-' vice 46, biases the control electrode 50 of electron discharge device 52 negative. In series with resistance 48 is a potential -m: of source 40 which is added to that impressed across 44 and causes 46 to break down with a lower total voltage across resistance 44.

When control electrode 50 is negative the current flow through anode resistance 54 of tube 52 is materially decreased and hence the control electrode of tube 56 becomes somewhat positive. When the control electrode of tube 56 becomes positive tube 56 draws a large current through resistance 58, across WhlCh, by virtue of the large current flow therethrough, there arises a. large potential.

Turning back to tube 36 it will be remembered that ordinarily there is high ne ative bias on its control electrode and accor ingly' there is very little anode current flowing therethrough. Across the control electrode and cathode of tube 36 there is applied, when a composite wave from A is present, a potential such as illustrated in Figure 6. Because of the negative bias on the grid of tube 36, the plate current therethrough will follow the solid line curve of Figure 7. The potential across resistance 44 may accordingly also be represented by the solid line curve of Figure 7.

Added to this is the voltage m), of potential source 40 as shown in Figure 7. This value is slightly lower than the extinction voltage of device 46.

Now, if the break down voltage 'of discharge device 46 is, as indicated on F i re .7, E5, it will be seen that current ows through resistance 48 during of the current flowing at the time 0 through resistance 48 is made such, or if the resistance 48 is chosen such that this value of current will cause blocking of tube 52, it will be seen that the anode current of tube 56 flowing through resistance 58 will suddenly increase to a maximum and continue to flow for periods of time corresponding to O P, O P etc. I

This is clearly shown in 'Fi e 8 where the plate current flowing in tug ted against time. The curve of Figure 8 may also represent the potentials arising across resistance 58. The high value of potential E will exist a length of time corresponding to a peak 0 AP of Figure 7 and bears a direct relation to the peak 0 A P; that is to say, it is directly proportional to the width of the peak 0 P or to the altitude of the peak AP.

e 56 is plotthen radiated over any suitable antenna 66.

- A source of positive potential 68 sup lies energy to the anode circuits of 56 an 62 through resistor 58. When the grid 56 is.

at a'blockin potential, no current flows to its anode. he current flowing to the anode of 62 is relativel small and causes only a slight potential d i-op across 58. Thus practically the whole of potential 68 isimpressed on the anode circuit of 62. Under this condition 62 and its associated circuits form an eflicient amplifier of the radio frequency circuits generated at 60 and the antenna 66 is energized.

.It will be seen, therefore, thatwhen a peak of current such as O A P of Figure 7 causes high current to flow in tube 56 and resistance 58, over a time corresponding to the line OP, a maximum potential will exist across resistor 58 which. will be of suflicient value to reduce the potential impressed on the anode circuits of 62 to a relatively low value. Under this condition,amplifier tube 62 and its. associated circuits cannot amplify the out put of generator 60 and antenna 66' will not be energized. Fi re 9 showsthe resultant antenna energizatlon and is the desired relation described in connection with Figures 3 and 4.

When point A of Figure 7 is reached, because of the shape of the carrier generated at B, the potential existing across resistance 58 suddenly drops to a minimum value and the antenna 66 is suddenly completely energized. The reason why the potential across resistance 58 drops suddenly is, of course, due to the fact that when the carrier reaches a point P of Figure 7 discharge device 46 suddenly becomes extinguished and as a result, tube '52 again suddenly becomes conducting which,

in turn, causes suddenreduction of plate current through tube 56.

In-this manner it will be clear that the carrier current generated at B is added to or combined with the composite wave generated at A; and, in accordance with the algebraic valueof the composite wave the antenna 66 is completely intermittently energized for periods of time having a definite relation to the peak values of the composite wave. It should, therefore, be clear that the antenna is energized in accordance with Figure 4 or, in other words, it is energized intermittently in accordance with the amplitudes of a signaling wave.

As described, a maximum positive value of composite wave causes minimum periods of energization. By reversing the input or output terminals of transformer 34,- a maximum period of energization of the antenna ma be had for a maximum value of potent1a the relationship depending upon the pomt, such as the primary of transformer 84, used as a reference point for the compos 1te wave. In either case, energization of the transmlt-ter bears a direct relation to the value of the amplitude of the composite wave, either a proportional one or an inverse proportional relation. With either relation of energ zation, the effect at the receiver is the same.

A suitable receivin system is disclosed in Figure 2. Antenna i4 is tuned to the frequency of oscillator 60 of Figure 1. The collected energy may be amplified at 76 and detected by any suitable means at 78. The output of detector 78 will have components havingfrequencies corresponding to the carrier frequency generated at B and corresponding to the tone frequencies generated at 2', 4', of Figure 1. By means of a filter 80 the dot or carrier frequencies may be eliminated and the output of filter 80 including frequencles 2, 4', 6' will simulate wave 8ofF1gure 3.

The output of filter 80 may be amplified by any suitable means such as amplifier 82 and, by additional filters 2, 4", 6", theoriginal tone frequencies 2, 4, 6, of Figure 3 may be obtained. These frequencies may be amplified by am lifiers 84, 86, 88 and trans-- lated into sound erably, run into ers, such as are well known art.

Many minor changes will, of course, readily suggest themselves to persons skilled in the art and accordingly the invention is not to be limited 'to the exact form described herein but it is to be limited solelyby the scope of the claims appended hereto. For example, the composite wave has been shown y phones 90, 92, 94 or prefin the telegraphic suitable high speed record-v to be made up of threesignal waves. Obviously any number of signal waves may be taken and a similar number of translators will then be used at the receiver.

The invention having been thus described what is claimed is:

1; In a multiplex signaling system means for generating a plurality of signal waves, means for modulating each signal wave in accordance with a si nal to be transmitted on each wave, means for combining the modulated waves so as to form a composite wave, and means comprising a glow discharge device and an electron discharge device for transmitting energy of a constant and higher frequency than any of the waves forming the composite wave intermittently at intervals corresponding to the algebraic amplitude of the composite wave.

2. In combination, a source of modulating energy, a source of carrier energy, an electron discharge device, means to combine and apply the carrier energy and modulating enl v discharge device, an impedance associated with the output circuit of the electron discharge device, a series combination of a glow discharge device and an impedance, in parallel with said first mentioned impedance whereby current flows intermittently through the glow discharge device in accordance with predetermined values of the combined energy applied to the electron discharge device, another electron discharge device having'its input terminals connected across the series combination of the glowdischarge device and impedance whereby anode current flows intermittently in accordance with the intermittent current flow through said glow discharge device, an impedance in the output circuit of said last mentioned electron discharge device, and means for utilizing variations in voltage across said last mentioned impedance to control the flow of high frequency signaling energy.

3. In combination, a source of modulating energy, a source of carrier energy, an electron discharge device, means to combine and apply the carrier energy and modulating energy to the input electrodes of the electron discharge device, a resistance associated with the output circuit of the electron discharge device, a series combination of a glow discharge device and a resistance, in parallel with said first mentioned resistance whereby current flows intermittently through the glow discharge device in accordance with predetermined values of the combined energy applied to the electron discharge device,

another electron discharge device having its input terminals connected across the series combination of the glow discharge device and resistance whereby anode current flows intermittently in accordance with the inter- -mittent current flow through said glow discharge device, a resistance 1n the output circuit of said last mentioned electron discharge device, and means for utilizin variations in voltage across said last mentioned resistance to.control the flow of high frequency signalin energy.

3 JAMES L. FINCH. 

